I think you're headed in the right direction. Typically the best way to implement something like this is to pass around a single variable reference (either an object or a hash reference are common) with all of your state information.

my $state = {
   username  => $username,
   sessionid => $sessionid,
   whatever  => $else,
};

&one($state, $other_args);
&two($state, @more);
&three($state);
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Another way of doing this is to turn $state into an object, and turn one, two and three into object methods.

$state = new Object($username, $sessionid);

$state->one($other_args);
$state->two(@more);
$state->three;
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I kind of like things like Class::Struct for defining a simple object-ish representation of a data structure like that, which is easy to pass around as a single unit.